Silicifiers are among the most important living organisms of planet Earth. They are able to take advantage of the abundance of silicon (silicon is the second-most-abundant element in the planet) to build silicified architectures, which in particular can help for protection against predators or for facilitating the penetration of light and nutrients to the cells.

This Research Topic focuses on the marine realm, for which numerous unknowns remain regarding the silica cycle. Marine diatoms vs. siliceous sponges and radiolarians rose to prominence about 100 M years ago. Today diatoms play a key role in the trophic networks of the most productive coastal or open-ocean ecosystems, as well as in the biology–mediated transfer of CO2 from the surface to the ocean interior (the so–called biological pump). The physiology and biochemistry of pelagic diatoms have been extensively studied but many gaps remain regarding the silicification mechanisms and their variations due to environmental change. The link between Si and C cycles also needs to be re-evaluated using new tools such as genomics. Moreover, benthic diatoms and their role in coastal ecosystems have been largely ignored despite first estimations that they could reach 40% of the coastal diatom production. In the same vein, the key role of other siliceous organisms in the silica cycle, such as benthic sponges has only been demonstrated at regional scale and needs to be quantified at a global ocean scale. Furthermore, the accumulation of silica by non siliceous pycocyanobacteria has been evidenced but the reasons and mechanisms behind such accumulation are still unidentified. Similarly the formation of siliceous elements in some nanoplanktonic flagellates such as the pelagic silicoflagellates or the elusive group of parmales, has also been reported yet remains to be quantified. The understanding of all these processes closely associated with the metabolism of such a diversity of silicifiers should now benefit from the use of genomics.

Since the year 2000, the genomes of some diatoms have been sequenced and genomics can now be used to formulate new hypotheses and research strategies for explaining the role of different silicifiers in coastal and open-open ecosystems and their control of C, N, P, and Si biogeochemical cycles. Our understanding of interactions between diatoms and other phytoplankton, at the cell/species level, and their consequences for nutrient cycles and ecosystem functioning is rapidly evolving. Genomics contributes to improved understanding such these processes. We might well be at a pivotal moment of the perception of the role of silicifiers in marine ecosystems and biogeochemicla cycles, as well as of the biology of ocean silicification processes.

We welcome papers addressing the following topics:
(1) the chemistry and physiology of silicification,
(2) the evolutionary history of marine silicifiers,
(3) the role of marine silicifiers in global biogeochemical cycles past-present-future.
We encourage in particular submission combining chemical, physiological and omic approaches in novel ways, as well as exploratory model studies.

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Frontiers in Marine Science

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